Antonyms of adj step-by-step

1 sense of step-by-step

Sense 1
bit-by-bit, in small stages, piecemeal, step-by-step, stepwise -- (one thing at a time)

INDIRECT (VIA gradual) -> sudden -- (happening without warning or in a short space of time; "a sudden storm"; "a sudden decision"; "a sudden cure")

Similarity of adj step-by-step

1 sense of step-by-step

Sense 1
bit-by-bit, in small stages, piecemeal, step-by-step, stepwise -- (one thing at a time)
       => gradual (vs. sudden) -- (proceeding in small stages; "a gradual increase in prices")

Synonyms of adv step-by-step

2 senses of step by step

Sense 1
gradually, bit by bit, step by step -- (in a gradual manner; "the snake moved gradually toward its victim")

Sense 2
stepwise, step by step -- (proceeding in steps; "the voltage was increased stepwise")